The present invention is directed toward small actuators for devices such as valves, and methods for forming and using such actuators.
Microvalves are miniature valves used to control fluid flows at low flow rates. Such valves and other micro-electromechanical (MEMS) devices are conventionally used in several industrial and professional applications where it is important to precisely regulate the flow of small quantities of gases or liquids. For example, microvalves are used for some types of medical research (such as DNA research), medical treatments, and other types of applications that involve metering fluids at low flow rates.
Some conventional microvalves are formed directly in a semiconductor substrate (such as silicon) using techniques generally similar to those used to form integrated circuits. Such valves typically include a flexible diaphragm that opens and closes a fluid orifice when selected voltages are applied to the valve. Examples of such valves are disclosed in U.S. Pat. No. 5,810,325 to Carr, which is incorporated herein in its entirety by reference.
One drawback with some conventional diaphragm microvalves of the type described above is that the valves may fail because the diaphragm can fracture or deform after repeated uses. Another drawback is that conventional diaphragms typically do not exert a large sealing force to close the fluid orifice. Accordingly, such diaphragms may not be suitable for valves that regulate high pressure fluids.
The present invention is directed toward actuators and methods for forming and using actuators. An actuator assembly in accordance with one aspect of the invention includes an actuator body having an actuator channel with a first end and a second end spaced apart from the first end. An actuator is disposed in the actuator channel and is movable when in a flowable state from a first position in the actuator channel to a second position in the actuator channel. Accordingly, the assembly can further include a heater positioned proximate to the actuator channel to heat the actuator from a solid state to a flowable state. In a further aspect of the invention, the actuator body can include a fluid passageway having an orifice in fluid communication with the actuator channel. Accordingly, the actuator can allow fluid to flow through the orifice when the actuator is in the first position and block the flow of fluid through the orifice when in the second position.
The invention is also directed toward a method for manufacturing an actuator. In one aspect of the invention, the method can include forming a channel in a substrate, positioning an actuator in the channel with the actuator being movable within the channel between a first position and a second position when the actuator is in a flowable state, and disposing an actuator heater adjacent to the channel with the actuator heater configured to at least partially liquify the actuator. The method can further include forming the channel to have a first region and at least one second region adjacent to the first region. The first region can have a first surface characteristic, and the second region can have a second surface characteristic different than the first surface characteristic. The actuator can have a first surface tension when in a flowable state and contacting the first region, and the actuator can have a second surface tension when in a flowable state and contacting the second region. The second surface tension can be greater than the first surface tension such that the actuator can halt its movement through the channel upon contacting the second region.
The invention is also directed toward a method for controlling an actuator. The method can include heating the actuator in an actuator channel from a solid state to a flowable state, moving the actuator in a first region of the actuator channel from a first position to a second position, and cooling the actuator to solidify the actuator in a second position. The method can further include halting the motion of the flowable actuator at the second position by engaging the actuator with a surface of a second region of the channel. For example, the actuator can have a surface tension when in contact with the second region that is higher than a surface tension of the actuator when in contact with the first region such that the actuator can halt its movement in the channel upon contacting the second region.